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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2014 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: AbstractKVStore.html 939 2015-05-29 01:16:17Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.jsimpledb.kv;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import java.util.Arrays;<a name="line.10"></a>
<span class="sourceLineNo">011</span>import java.util.Iterator;<a name="line.11"></a>
<span class="sourceLineNo">012</span><a name="line.12"></a>
<span class="sourceLineNo">013</span>import org.jsimpledb.util.ByteReader;<a name="line.13"></a>
<span class="sourceLineNo">014</span>import org.jsimpledb.util.ByteUtil;<a name="line.14"></a>
<span class="sourceLineNo">015</span>import org.jsimpledb.util.ByteWriter;<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>/**<a name="line.17"></a>
<span class="sourceLineNo">018</span> * Support superclass for {@link KVStore} implementations.<a name="line.18"></a>
<span class="sourceLineNo">019</span> *<a name="line.19"></a>
<span class="sourceLineNo">020</span> * &lt;p&gt;<a name="line.20"></a>
<span class="sourceLineNo">021</span> * This class provides a partial implementation via the following methods:<a name="line.21"></a>
<span class="sourceLineNo">022</span> * &lt;ul&gt;<a name="line.22"></a>
<span class="sourceLineNo">023</span> *  &lt;li&gt;A {@link #get get()} implementation based on {@link #getAtLeast getAtLeast()}&lt;/li&gt;<a name="line.23"></a>
<span class="sourceLineNo">024</span> *  &lt;li&gt;{@link #getAtLeast getAtLeast()} and {@link #getAtMost getAtMost()} implementations based on<a name="line.24"></a>
<span class="sourceLineNo">025</span> *      {@link #getRange getRange()}.&lt;/li&gt;<a name="line.25"></a>
<span class="sourceLineNo">026</span> *  &lt;li&gt;A {@link #remove remove()} implementation that delegates to {@link #removeRange removeRange()}.&lt;/li&gt;<a name="line.26"></a>
<span class="sourceLineNo">027</span> *  &lt;li&gt;A {@link #removeRange removeRange()} implementation that delegates to {@link #getRange getRange()},<a name="line.27"></a>
<span class="sourceLineNo">028</span> *      iterating through the range of keys and removing them one-by-one via {@link Iterator#remove}.&lt;/li&gt;<a name="line.28"></a>
<span class="sourceLineNo">029</span> *  &lt;li&gt;{@link #encodeCounter encodeCounter()}, {@link #decodeCounter encodeCounter()}, and<a name="line.29"></a>
<span class="sourceLineNo">030</span> *      {@link #adjustCounter adjustCounter()} implementations using normal reads and writes<a name="line.30"></a>
<span class="sourceLineNo">031</span> *      of values in big-endian encoding (does not provide any lock-free behavior).&lt;/li&gt;<a name="line.31"></a>
<span class="sourceLineNo">032</span> *  &lt;li&gt;A {@link #put put()} implementation throwing {@link UnsupportedOperationException}&lt;/li&gt;<a name="line.32"></a>
<span class="sourceLineNo">033</span> * &lt;/ul&gt;<a name="line.33"></a>
<span class="sourceLineNo">034</span> *<a name="line.34"></a>
<span class="sourceLineNo">035</span> * &lt;p&gt;<a name="line.35"></a>
<span class="sourceLineNo">036</span> * Therefore, a read-only {@link KVStore} implementation is possible simply by implementing {@link #getRange}.<a name="line.36"></a>
<span class="sourceLineNo">037</span> * &lt;/p&gt;<a name="line.37"></a>
<span class="sourceLineNo">038</span> */<a name="line.38"></a>
<span class="sourceLineNo">039</span>public abstract class AbstractKVStore implements KVStore {<a name="line.39"></a>
<span class="sourceLineNo">040</span><a name="line.40"></a>
<span class="sourceLineNo">041</span>    protected AbstractKVStore() {<a name="line.41"></a>
<span class="sourceLineNo">042</span>    }<a name="line.42"></a>
<span class="sourceLineNo">043</span><a name="line.43"></a>
<span class="sourceLineNo">044</span>    @Override<a name="line.44"></a>
<span class="sourceLineNo">045</span>    public byte[] get(byte[] key) {<a name="line.45"></a>
<span class="sourceLineNo">046</span>        final KVPair pair = this.getAtLeast(key);<a name="line.46"></a>
<span class="sourceLineNo">047</span>        return pair != null &amp;&amp; Arrays.equals(pair.getKey(), key) ? pair.getValue() : null;<a name="line.47"></a>
<span class="sourceLineNo">048</span>    }<a name="line.48"></a>
<span class="sourceLineNo">049</span><a name="line.49"></a>
<span class="sourceLineNo">050</span>    @Override<a name="line.50"></a>
<span class="sourceLineNo">051</span>    public KVPair getAtLeast(byte[] minKey) {<a name="line.51"></a>
<span class="sourceLineNo">052</span>        final Iterator&lt;KVPair&gt; i = this.getRange(minKey, null, false);<a name="line.52"></a>
<span class="sourceLineNo">053</span>        try {<a name="line.53"></a>
<span class="sourceLineNo">054</span>            return i.hasNext() ? i.next() : null;<a name="line.54"></a>
<span class="sourceLineNo">055</span>        } finally {<a name="line.55"></a>
<span class="sourceLineNo">056</span>            this.closeIfPossible(i);<a name="line.56"></a>
<span class="sourceLineNo">057</span>        }<a name="line.57"></a>
<span class="sourceLineNo">058</span>    }<a name="line.58"></a>
<span class="sourceLineNo">059</span><a name="line.59"></a>
<span class="sourceLineNo">060</span>    @Override<a name="line.60"></a>
<span class="sourceLineNo">061</span>    public KVPair getAtMost(byte[] maxKey) {<a name="line.61"></a>
<span class="sourceLineNo">062</span>        final Iterator&lt;KVPair&gt; i = this.getRange(null, maxKey, true);<a name="line.62"></a>
<span class="sourceLineNo">063</span>        try {<a name="line.63"></a>
<span class="sourceLineNo">064</span>            return i.hasNext() ? i.next() : null;<a name="line.64"></a>
<span class="sourceLineNo">065</span>        } finally {<a name="line.65"></a>
<span class="sourceLineNo">066</span>            this.closeIfPossible(i);<a name="line.66"></a>
<span class="sourceLineNo">067</span>        }<a name="line.67"></a>
<span class="sourceLineNo">068</span>    }<a name="line.68"></a>
<span class="sourceLineNo">069</span><a name="line.69"></a>
<span class="sourceLineNo">070</span>    @Override<a name="line.70"></a>
<span class="sourceLineNo">071</span>    public void put(byte[] key, byte[] value) {<a name="line.71"></a>
<span class="sourceLineNo">072</span>        throw new UnsupportedOperationException();<a name="line.72"></a>
<span class="sourceLineNo">073</span>    }<a name="line.73"></a>
<span class="sourceLineNo">074</span><a name="line.74"></a>
<span class="sourceLineNo">075</span>    @Override<a name="line.75"></a>
<span class="sourceLineNo">076</span>    public void remove(byte[] key) {<a name="line.76"></a>
<span class="sourceLineNo">077</span>        this.removeRange(key, ByteUtil.getNextKey(key));<a name="line.77"></a>
<span class="sourceLineNo">078</span>    }<a name="line.78"></a>
<span class="sourceLineNo">079</span><a name="line.79"></a>
<span class="sourceLineNo">080</span>    @Override<a name="line.80"></a>
<span class="sourceLineNo">081</span>    public void removeRange(byte[] minKey, byte[] maxKey) {<a name="line.81"></a>
<span class="sourceLineNo">082</span>        final Iterator&lt;KVPair&gt; i = this.getRange(minKey, maxKey, false);<a name="line.82"></a>
<span class="sourceLineNo">083</span>        try {<a name="line.83"></a>
<span class="sourceLineNo">084</span>            while (i.hasNext()) {<a name="line.84"></a>
<span class="sourceLineNo">085</span>                i.next();<a name="line.85"></a>
<span class="sourceLineNo">086</span>                i.remove();<a name="line.86"></a>
<span class="sourceLineNo">087</span>            }<a name="line.87"></a>
<span class="sourceLineNo">088</span>        } finally {<a name="line.88"></a>
<span class="sourceLineNo">089</span>            this.closeIfPossible(i);<a name="line.89"></a>
<span class="sourceLineNo">090</span>        }<a name="line.90"></a>
<span class="sourceLineNo">091</span>    }<a name="line.91"></a>
<span class="sourceLineNo">092</span><a name="line.92"></a>
<span class="sourceLineNo">093</span>    @Override<a name="line.93"></a>
<span class="sourceLineNo">094</span>    public byte[] encodeCounter(long value) {<a name="line.94"></a>
<span class="sourceLineNo">095</span>        final ByteWriter writer = new ByteWriter(8);<a name="line.95"></a>
<span class="sourceLineNo">096</span>        ByteUtil.writeLong(writer, value);<a name="line.96"></a>
<span class="sourceLineNo">097</span>        return writer.getBytes();<a name="line.97"></a>
<span class="sourceLineNo">098</span>    }<a name="line.98"></a>
<span class="sourceLineNo">099</span><a name="line.99"></a>
<span class="sourceLineNo">100</span>    @Override<a name="line.100"></a>
<span class="sourceLineNo">101</span>    public long decodeCounter(byte[] value) {<a name="line.101"></a>
<span class="sourceLineNo">102</span>        if (value.length != 8)<a name="line.102"></a>
<span class="sourceLineNo">103</span>            throw new IllegalArgumentException("invalid encoded counter value: length = " + value.length + " != 8");<a name="line.103"></a>
<span class="sourceLineNo">104</span>        return ByteUtil.readLong(new ByteReader(value));<a name="line.104"></a>
<span class="sourceLineNo">105</span>    }<a name="line.105"></a>
<span class="sourceLineNo">106</span><a name="line.106"></a>
<span class="sourceLineNo">107</span>    @Override<a name="line.107"></a>
<span class="sourceLineNo">108</span>    public void adjustCounter(byte[] key, long amount) {<a name="line.108"></a>
<span class="sourceLineNo">109</span>        if (key == null)<a name="line.109"></a>
<span class="sourceLineNo">110</span>            throw new NullPointerException("null key");<a name="line.110"></a>
<span class="sourceLineNo">111</span>        final byte[] previous = this.get(key);<a name="line.111"></a>
<span class="sourceLineNo">112</span>        if (previous == null)<a name="line.112"></a>
<span class="sourceLineNo">113</span>            return;<a name="line.113"></a>
<span class="sourceLineNo">114</span>        this.put(key, this.encodeCounter(this.decodeCounter(previous) + amount));<a name="line.114"></a>
<span class="sourceLineNo">115</span>    }<a name="line.115"></a>
<span class="sourceLineNo">116</span><a name="line.116"></a>
<span class="sourceLineNo">117</span>    private void closeIfPossible(Iterator&lt;KVPair&gt; i) {<a name="line.117"></a>
<span class="sourceLineNo">118</span>        if (i instanceof AutoCloseable) {<a name="line.118"></a>
<span class="sourceLineNo">119</span>            try {<a name="line.119"></a>
<span class="sourceLineNo">120</span>                ((AutoCloseable)i).close();<a name="line.120"></a>
<span class="sourceLineNo">121</span>            } catch (Exception e) {<a name="line.121"></a>
<span class="sourceLineNo">122</span>                // ignore<a name="line.122"></a>
<span class="sourceLineNo">123</span>            }<a name="line.123"></a>
<span class="sourceLineNo">124</span>        }<a name="line.124"></a>
<span class="sourceLineNo">125</span>    }<a name="line.125"></a>
<span class="sourceLineNo">126</span>}<a name="line.126"></a>
<span class="sourceLineNo">127</span><a name="line.127"></a>




























































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